How we select the resurfacing There’s information on our website treatment for your street Wellington.govt.nz Why we chipseal If you have other questions, your road When deciding which type of resurfacing to use, we email [email protected] or phone 499 4444. carry out two surveys of the entire roading network. Our postal address is: One survey assesses the condition of the existing Transport Assets, Wellington City Council surface and records things like cracking, potholes, PO Box 2199, Wellington 6140 broken edges and patching.

The other survey measures road ‘roughness’ – using a number of lasers attached to a vehicle. These surveys are entered into our road assessment and maintenance management system which helps to identify which sections of the network need waterproofing and which need reshaping. A benefit/ cost analysis, which takes into account traffic volumes, pavement loadings, and the results of the ‘roughness’ survey, is an integral part of the system. Bearing in mind that the New Zealand Transport Agency provides nearly half of the funding for the city’s road resurfacing programme each year, the Council has an obligation to ratepayers and taxpayers to ensure that the best engineering options and the most cost-effective solution is chosen in each case.

Most of our suburban streets have a flexible structure requiring periodic waterproofing – and chipseal is the best engineering solution for this. Chipseal provides a flexible, waterproof, highly skid-resistant surface. While it’s true that chipseal in suburban streets can cause some inconvenience, if we were to use the smoother asphaltic concrete seal then the cost would be more than three to five times as much – none of which, in the present climate, would be likely to be subsidised by NZTA. CSWCC99363 Why we resurface roads What’s the difference?

Keeping Wellington City’s roads in good shape so Chipseals are primarily used to prevent we can all get where we want to go is a crucial part water entering and damaging the underlying of the maintenance work Wellington City Council foundation layers and generally have a life does every year to keep the city moving. of three to 10 years. Their use can be likened to painting your house on a regular basis to Road surfaces are not permanent – they deteriorate prevent the weatherboards rotting. over time. Wear and tear from traffic, trenching work for underground services and oxidation of Asphaltic concrete is used to improve the the surface from sunlight all take a toll. As a result, smoothness of ride for people in vehicles we have to periodically resurface roads to ensure and on bikes and also helps reduce vehicle the underlying foundations do not deteriorate and maintenance costs. Asphaltic concrete is not then need expensive and disruptive remedial work. as waterproof as chipseal unless it is used in thick layers – usually over 60mm. On average, we resurface about 68km of road every year – about 10 percent of the city’s 690km There is usually some ‘give’ in the underlying of roads. layers or foundations of most of our roads. In other words they flex under heavy loads – so it It mostly happens between November and March is not wise to cover them in thick layers of seal because warm air and ground temperatures are in most situations – because the seal will crack essential to get the best results. and disintegrate. We use asphaltic concrete extensively in the inner city and in shopping Resurfacing treatments centres because of traffic volumes and high pedestrian flows. Like other urban local authorities around the country, we use three main treatments for Slurry seal has been used in increasing resurfacing roads: quantities in residential streets over the last few years as the advantages include a smoother • Chipseal – consists of a layer of sprayed bitumen surface with fewer problems caused by loose followed by one or two layers of chip chips. However slurry seals have limitations. • Asphaltic concrete (AC) – is a hot-applied They have a shorter life cycle than chipseals mixture of chip and bitumen and are also very brittle, which makes them unsuitable for cracked or highly flexible roads. • Slurry Seal – is a thin cold-applied mixture of bitumen and chip.